CN110914100A

CN110914100A - Wireless charging system

Info

Publication number: CN110914100A
Application number: CN201880050187.2A
Authority: CN
Inventors: F.托姆贝利
Original assignee: ABB Schweiz AG
Current assignee: ABB AS Norway
Priority date: 2017-07-28
Filing date: 2018-07-25
Publication date: 2020-03-24
Also published as: US20200161901A1; EP3658406B1; EP3658406A1; WO2019020710A1; US11427095B2

Abstract

A wireless charging system (12) for an electric vehicle (13) comprising: an AC-to-DC converter (14) connectable to an AC electrical grid (18); a DC to AC converter (24) interconnected with the AC to DC converter (14); a first induction coil (26) interconnected with the DC to AC converter (24) and for inductively coupling to a second induction coil (30) for power transfer via the air gap; a first housing (16), an AC to DC converter (14) disposed in the first housing (16); a second housing (22), a DC to AC converter (24) and an induction coil (26) being disposed in the second housing (22); and a cable (20) for interconnecting the AC-to-DC converter (14) and the DC-to-AC converter (24) outside the first housing (16) and the second housing (22).

Description

Wireless charging system

Technical Field

The present invention relates to the field of electric vehicles. In particular, the present invention relates to a wireless charging system and charging system arrangement for an electric vehicle.

Background

Wireless power transfer via an induction coil is an emerging technology that can enable electrical power transfer over a particular distance without physical contact. In recent years, the transmission distance of kilowatt power levels has increased from a few millimeters to hundreds of millimeters with grid-to-load efficiencies above 90%. These advances make wireless power transfer very attractive for charging of electric vehicles in both stationary and dynamic charging scenarios.

Batteries of electric vehicles are typically charged on the grid. After rectification and stabilization by the converter system, the supplied power is transferred into the high-voltage system of the electric vehicle with inductive transmission. Inductive energy transfer generally has the advantage of being a robust and convenient method of energy transfer, compared to other energy transfer processes such as conductive or cable-bound charging.

The inductive transmission device typically comprises two inductive coils, wherein a first inductive coil is provided by the wireless charging device and a second inductive coil is provided by the electric vehicle. Both coils can be considered as air transformers.

It is possible that the first induction coil is arranged remote from the converter system, since it may be provided, for example, below a parking lot of the electric vehicle. The power transfer between the converter system and the first induction coil can then take place via litz wire. Litz wire may be required due to the high switching frequency of the voltage used by the converter system to supply the first induction coil. However, litz wire can be quite expensive.

US 20150022142 a1 allows for the integration of electronics components inside the receiver of an inductive power transfer system.

US 20130038279 a1 describes the integration of electronics within an inductive power transfer system to reduce EMC (electromagnetic compatibility).

US 2013214591 a1 shows a charging station for charging an electric vehicle via high-frequency power transmission between two coils. The charging station comprises an AC-DC converter with a buck-boost converter connected to a DC power transfer cable and a point-of-load converter for generating a high-frequency current in the transmission coil. One AC-DC converter may be connected to several points of the load converter.

US 2009121675 a1 relates to a control method for an inductive battery charging device. Several topologies for AC-DC converters and DC-AC converters are mentioned and the DC link voltage can be controlled.

Disclosure of Invention

An object of the present invention is to provide an economical and efficient wireless charging system for electric vehicles.

This object is achieved by the subject matter of the independent claims. Further exemplary embodiments are apparent from the dependent claims and the following description.

One aspect of the present invention relates to a wireless charging system for an electric vehicle. The electric vehicle may be a street vehicle that may be driven by an electric motor powered by a battery. The wireless charging system may be used to charge a battery. Hybrid vehicles, i.e. vehicles having an internal combustion engine and an electric motor, may also be considered electric vehicles.

According to an embodiment of the invention, a charging system comprises an AC-to-DC converter connectable to an AC grid; a DC to AC converter interconnected with the AC to DC converter; a first inductive coil interconnected with the DC-to-AC converter and for inductively coupling to a second inductive coil via an air gap for power transfer; a first housing in which the AC-to-DC converter is disposed; a second housing in which the DC to AC converter and induction coil are disposed; and a cable for interconnecting the AC-to-DC converter and the DC-to-AC converter outside the first housing and the second housing.

In other words, an AC-to-AC converter for converting the AC grid voltage into an AC voltage supplied to the first induction coil, which AC-to-AC converter consists of an AC-to-DC converter and a DC-to-AC converter, is distributed between the two housings. The first housing, which may be disposed remotely from the second housing, houses an AC to DC converter, and the second housing, which may have to be disposed in the vicinity of an electric vehicle, houses a DC to AC converter. For example, the second housing may be located in a ground surface below the electric vehicle, such as a parking lot. In this way, the length of the electrical interconnection between the DC-to-DC converter and the first induction coil can be made relatively short. For the cable interconnecting the two housings, a common cable adapted to carry DC current may be used.

In addition, since it is not necessary to transfer the AC current over a larger distance, the AC current may have a frequency larger than 10 kHz, and thus electromagnetic interference to the environment may be reduced compared to the solution using litz wires. The EMC of the system can be increased.

The first and second induction coils separated by an air gap may be adapted and arranged for use in an inductive energy transfer device. Both the first and second induction coils may be pancake coils that may be arranged substantially parallel to each other. It has to be noted that the second induction coil is arranged outside the second housing, for example in the bottom of the electric vehicle. With such an air transformer, energy can be transferred across distances of several decimeters. A time-varying magnetic field is generated with the first induction coil. A portion of the magnetic field flows through the second induction coil and induces a current. The second induction coil may be connected to a battery of the electric vehicle via a rectifier, and then the battery may be charged.

The wireless charging system further includes: a first controller inside the first housing for controlling the AC to DC converter; and a second controller inside the second housing for controlling the DC to AC converter. The first controller may control an AC-to-DC converter (such as a boost converter) for generating a DC voltage in the DC link. The second controller may control a DC-to-AC converter (such as a full bridge converter) for generating an AC voltage from the DC voltage to be supplied to the first induction coil. For example, the AC voltage provided to the first induction coil may be pulse width modulated and/or may have a variable frequency to control power transfer efficiency. The fundamental frequency of the DC to AC converter may be about 85 kHz and/or may be varied to a limited extent to achieve optimum efficiency.

Further, the first controller and the second controller are communicatively interconnected with a signal line provided in the cable. The controller may be interconnected with a signal line, which may be provided in the same cable jacket (jack) as the cable used to pass the DC current between the two housings. No electromagnetic shielding between the DC current cable and the signal line may be necessary.

With the communication connection, the control of the switching frequency, the power transfer and/or the DC-link voltage may be synchronized between the first controller and the second controller.

Also, the error signal may be transmitted between the first controller and the second controller via a signal line. In case of an error, both converters may be switched off.

According to an embodiment of the invention, the first controller and/or the second controller is adapted to control the power transfer between the AC-to-DC converter and the DC-to-AC converter by changing a DC-link voltage of a DC-link between the AC-to-DC converter and the DC-to-AC converter. The DC link voltage may not be controlled to a fixed voltage but may be variable. This is possible because due to the comparatively short distance between the DC-to-AC converter and the second induction coil, the power transfer there can also be controlled in a more flexible manner.

According to an embodiment of the invention, the first controller is adapted to control the DC-link voltage to a variable setpoint voltage. The height of the setpoint voltage may determine the power delivered to the DC to AC converter inside the second housing.

According to an embodiment of the invention, the first controller receives a power demand of the second controller via a signal line and determines the variable set point voltage in accordance with the power demand.

According to an embodiment of the invention, the wireless charging system further comprises at least two second housings, wherein each second housing comprises a DC-to-AC converter interconnected with the AC-to-DC converter and comprises an induction coil interconnected with the DC-to-AC converter. In other words, more than one charging adapter consisting of a first induction coil and a DC-to-AC converter within a common housing may be interconnected with an AC-to-DC converter provided in the first housing. The charging adapters may all be connected to the same DC link.

According to an embodiment of the invention, a second controller is arranged inside each second housing for controlling the DC-to-AC converter inside the respective housing. Also in this case, the signal line from each second controller to the first controller may be arranged inside a DC cable interconnecting the respective DC-to-AC converter and the AC-to-DC converter.

According to an embodiment of the invention, the first controller receives a power demand of the second controller via a signal line and determines the variable set point voltage in accordance with the power demand. For example, the power requirements may be summed and the setpoint voltage may be calculated therefrom.

According to an embodiment of the invention, each second controller is adapted to control the duty cycle and/or the frequency of the AC voltage supplied to the first induction coil. With the duty cycle and/or frequency, the power supplied to the first induction coil can be controlled. The power may be equal to the power demand communicated to the first controller.

According to an embodiment of the invention, the second housing is a ground adapter for placement in a surface of a parking lot for an electric vehicle. The second housing may have a flat body and/or the first induction coil may be a substantially flat coil arranged inside the flat body.

According to an embodiment of the invention, a compensation capacitor is arranged inside the second housing, the compensation capacitor being interconnected between the DC-to-AC converter and the first induction coil. The first induction coil and the compensation capacitor may form an oscillating circuit. The second induction coil and the corresponding compensation capacitor may also form such an oscillating circuit. The two tank circuits may resonate to improve power transfer. In this way, an efficient energy transfer of up to 95% can be achieved.

According to an embodiment of the invention, a DC-link with a DC-link capacitor is arranged inside the first housing, the DC-link being interconnected between the AC-to-DC converter and the DC-to-AC converter. Such a DC-link capacitor may stabilize the voltage in the DC-link. Furthermore, when more than one DC-to-AC converter with interconnected first coils is connected to the AC-to-DC converter, the DC link capacitor inside the first housing may be shared.

There are several possible topologies for AC-to-DC converters and DC-to-AC converters, however, the topologies are not limited by the following embodiments.

According to an embodiment of the invention, the DC-to-AC converter is a full bridge converter. A full-bridge converter may comprise a half-bridge for each phase of the converter. The half bridge may comprise two series connected switching devices, such as transistors or thyristors.

Generally, an AC to DC converter may be an active front end or a passive front end. It may be a single-phase or a three-phase converter.

According to an embodiment of the invention, the AC-to-DC converter comprises a boost converter and/or a passive rectifier. The boost converter may include an inductor connected in series with the diode and a switching device, such as a transistor or thyristor, connected between the inductor and the diode. The passive rectifier may generate a DC voltage that is boosted by the boost converter.

According to an embodiment of the invention, the AC-to-DC converter comprises a full bridge converter. It has to be noted that the AC-to-DC converter may be a single-phase or a three-phase converter. The DC to AC converter may be a single phase converter.

Furthermore, the AC to DC converter may comprise a passive input filter, which may consist of an inductance and/or a capacitor.

Further aspects of the invention relate to a charging system arrangement comprising a wireless charging system as described above and in the following and an electric vehicle having a second induction coil inductively coupled with a first induction coil provided by the wireless charging system. The electric vehicle may be adapted to be charged by a wireless charging system. The second induction coil may be connected with a battery of the electric vehicle via a passive rectifier.

According to an embodiment of the present invention, the second housing is placed in the ground under the electric vehicle, and the second induction coil is provided at the bottom side of the electric vehicle. The cable interconnecting the second housing with the first housing may also be at least partially in the ground.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

Drawings

The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments illustrated in the drawings.

Fig. 1 schematically shows a charging system arrangement according to an embodiment of the invention.

Fig. 2 schematically illustrates a wireless charging system according to an embodiment of the present invention.

Fig. 3 schematically shows a wireless charging system according to a further embodiment of the invention.

Fig. 4 shows a schematic circuit diagram of an AC-to-DC converter of a wireless charging system according to an embodiment of the invention.

Fig. 5 shows a schematic circuit diagram of a further AC-to-DC converter of the wireless charging system according to an embodiment of the present invention.

Fig. 6 shows a schematic circuit diagram of a DC-to-AC converter of a wireless charging system according to an embodiment of the invention.

Fig. 7 shows a schematic circuit diagram of a rectifier used in a charging system arrangement according to an embodiment of the invention.

The reference symbols used in the drawings and their meanings are listed in the list of reference symbols in summary form. In principle, identical parts are provided with the same reference symbols in the figures.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Fig. 1 shows a charging system arrangement 10 comprising a wireless charging system 12 and an electric vehicle 13.

The wireless charging system 12 includes an AC-to-DC converter 14 in a first housing 16 that converts AC current from a power grid 18 to DC current. The DC current is transferred from the first housing 16 to a second housing 22 via the cable 20, the second housing 22 housing a DC to AC converter 24 and a first induction coil 26.

The first housing 16 may be connected to a wall, for example. The second housing 22 may be disposed in a ground 27 below the electric vehicle 13, such as in a parking lot.

The DC-to-AC converter generates a high frequency current, which is supplied to the first induction coil.

The first induction coil 26 is inductively coupled with a second induction coil 28 in an onboard charging device 30 of the electric vehicle 13. The AC current induced in the second induction coil 28 is rectified by a rectifier 32 inside the electric vehicle 13 and supplied to a battery 34 of the electric vehicle 13.

Fig. 2 shows the wireless charging system 12 in more detail. It can be seen that in addition to the AC-to-DC converter 14, a controller 36 for the AC-to-DC converter 14 and a DC link 38 having a DC link capacitor 40 are disposed inside the first housing 16.

In the second housing 22, a compensation capacitor 42 is interconnected between the DC to AC converter 24 and the first induction coil 26 for forming a resonant circuit. Further, a controller 44 for the DC to AC converter 24 is arranged in the second housing 22.

The first and

second controllers

36, 44 are interconnected with a signal wire 46, which signal wire 46 may be guided in the same cable sheath as the cable 20 for conducting DC current between the first and

second housings

16, 22.

The first controller 36 controls the switching devices of the AC-to-DC converter to generate a DC current of varying voltage in the DC link 38.

The second controller 44 controls the switching devices of the DC-to-AC converter 24 to convert the varying voltage in the DC link 38 into a high frequency current that is supplied to the first induction coil 26. The second controller 44 may control the duty cycle and/or frequency of the AC voltage provided to the first induction coil 26. For example, the voltage in the power grid 18 may have a voltage of 50 Hz or 60 Hz. On the other hand, the pulse width modulated current and/or the AC voltage in the first induction coil may have a frequency of more than 10 kHz. To control the transfer of power from the AC to DC converter to the DC to AC converter via the DC link 38 and/or the transfer of power from the DC to AC converter into the first induction coil 26, the

controllers

36, 44 may exchange information, such as the power demand to be supplied to the electric vehicle, via the signal line 46.

As shown in fig. 2, the in-vehicle charging device 30 may also have a compensation capacitor 48 interconnected between the rectifier 32 and the second induction coil 28 for forming a resonant circuit.

Fig. 3 shows that more than one housing 22 may be connected with the first housing 16 using the DC current conducting cable 20. It must be understood that the housing 22 shown in fig. 3 may entirely contain the components shown in fig. 2 and/or described above and below.

It is possible that the first controller 36 in the first housing 16 controls the DC link voltage of the DC link 20 to a variable setpoint voltage that is dependent on the power demand of the DC to AC converter 24 in the second housing 22. All of these converters 24 may be connected to the DC link 40 via the cable 20 and/or may be controlled by a second controller 44 in the housing 22.

First controller 36 may receive power demands from each of second controllers 44 via signal line 46, and may determine a variable set point voltage based on these power demands. The power output of each DC-to-AC converter 24 may be controlled via the frequency and/or duty cycle of the AC voltage supplied to the respective first induction coil 26. The total power output may be controlled by the DC link voltage.

Fig. 4 shows an example of the AC-to-DC converter 14, the AC-to-DC converter 14 being composed of a passive rectifier 50 and a boost converter 52. The passive rectifier 50 comprises two diode half bridges. The boost converter 52 comprises three parallel arms of an inductor connected in series with a diode and a switching device 54 connected between the inductor and the diode. The switching device 54 may be controlled by the controller 36.

Fig. 5 shows a further example of an AC-to-DC converter 14, said AC-to-DC converter 14 consisting of a passive input filter 56 and a three-phase full-bridge converter 58. The passive input filter 56 comprises three single phase LC filters connected in star via capacitors. The full-bridge inverter 58 comprises three half-bridges of switching devices 54 connected in series. The switching device 54 may be controlled by the controller 36.

Fig. 6 shows an example of the DC-to-AC converter 24, which DC-to-AC converter 24 is a single-phase full-bridge converter. The DC-to-AC converter 24 comprises two half-bridges of switching devices 54 connected in series. The switching device 54 may be controlled by the controller 44.

Fig. 7 shows an example of a rectifier 32 that may be employed in the vehicle-mounted charging device 30. The rectifier comprises a passive rectifier 60 consisting of two diode half-bridges and a CLC output filter 62. The diode may prevent reverse current flow from the battery 34 to the rectifier 32.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or controller or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope.

REFERENCE SIGNS LIST

10 charging system arrangement

12 wireless charging system

13 electric vehicle

14 AC-to-DC converter

16 first casing

18 electric network

20 cable

22 second housing

24 DC-to-AC converter

26 first induction coil

27 ground and parking lot

28 second induction coil

30 vehicle-mounted charging device

32 rectifier

34 cell

36 first controller

38 DC link

40 DC link capacitor

42 compensating capacitor

44 second controller

46 signal line

48 compensating capacitor

50 passive rectifier

52 boost converter

54 switching device

56 input filter

58 three-phase full-bridge converter

60 passive rectifier

62 output filter

Claims

1. A wireless charging system (12) for an electric vehicle (13), the charging system (12) comprising:

an AC-to-DC converter (14) connectable to an AC electrical grid (18);

a DC to AC converter (24) interconnected with the AC to DC converter (14);

a first induction coil (26) interconnected with the DC to AC converter (24) and for inductively coupling to a second induction coil (28) for power transfer via an air gap;

a first housing (16), the AC-to-DC converter (14) being disposed in the first housing (16);

a second housing (22), the DC to AC converter (24) and the first induction coil (26) being disposed in the second housing (22);

a cable (20) for interconnecting the AC-to-DC converter (14) and the DC-to-AC converter (24) outside the first housing (16) and the second housing (22);

a first controller (36) inside the first housing (16) for controlling the AC to DC converter (14);

a second controller (44) inside the second housing (22) for controlling the DC to AC converter (24);

wherein the first controller (36) and the second controller (44) are communicatively interconnected with a signal line (46) provided in the cable (20).

2. The wireless charging system (12) of claim 1,

wherein the first controller (36) and/or the second controller (44) is adapted to control power transfer between the AC-to-DC converter (14) and the DC-to-AC converter (24) by varying a DC link voltage of a DC link (38) between the AC-to-DC converter (14) and the DC-to-AC converter (24).

3. The wireless charging system (12) of claim 1 or 2,

wherein the first controller (36) is adapted to control the DC-link voltage to a variable setpoint voltage.

4. The wireless charging system according to claim 3,

wherein the first controller (36) receives a power demand of the second controller (44) via the signal line (46) and determines the variable set point voltage in accordance with the power demand.

5. The wireless charging system (12) according to any one of the preceding claims, further comprising;

at least two second housings (22);

wherein each second housing (22) comprises a DC-to-AC converter (24) interconnected with the AC-to-DC converter (14) and comprises a first induction coil (26) interconnected with the DC-to-AC converter (24);

wherein a second controller (44) is arranged inside each second housing (22) for controlling the DC-to-AC converter (24) inside the respective housing (22).

6. The wireless charging system according to claim 5,

7. The wireless charging system of any one of the preceding claims,

wherein the second controller (44) is adapted to control the duty cycle and/or frequency of the AC voltage provided to the first induction coil (26).

8. The wireless charging system (12) of any one of the preceding claims,

wherein the second housing (22) is a ground adapter for placement in a ground (27) of a parking lot for an electric vehicle (13).

9. The wireless charging system (12) of any one of the preceding claims,

wherein a compensation capacitor (42) is arranged inside the second housing (22), the compensation capacitor (42) being interconnected between the DC-to-AC converter (24) and the first induction coil (26).

10. The wireless charging system (12) of any one of the preceding claims,

wherein a DC link (38) having a DC link capacitor (40) is arranged inside the first housing (16), the DC link (38) being interconnected between the AC-to-DC converter (14) and the DC-to-AC converter (24).

11. The wireless charging system (12) of any one of the preceding claims,

wherein the DC-to-AC converter (24) is a full bridge converter.

12. The wireless charging system (12) of any one of the preceding claims,

wherein the AC-to-DC converter (14) comprises a boost converter (52) and/or a passive rectifier (50).

13. The wireless charging system (12) of any one of the preceding claims,

wherein the AC-to-DC converter (14) comprises a full-bridge converter (58).

14. A charging system arrangement (10) comprising:

the wireless charging system (12) of any one of the preceding claims;

an electric vehicle (13) having a second inductive coil (28) inductively coupled with the first inductive coil (26) provided by the wireless charging system (12), wherein the electric vehicle (13) is adapted to be charged by the wireless charging system (12).

15. Charging system arrangement (10) according to claim 14,

wherein the second housing (22) is placed in a ground (27) below the electric vehicle (13) and the second induction coil (28) is provided at a bottom side of the electric vehicle (13).